# Free42 — HP-42S Calculator Simulator

> HP-42S calculator and HP-82240 printer simulator. (iPhone/iPad app by Thomas Okken.)

- Source: https://appshunter.io/ios/app/free42/id337692629 (this page in markdown: same URL + `.md`)
- Developer: [Thomas Okken](https://appshunter.io/developer/337692632)
- Category: Utilities
- Price: Free
- Rating: 4.80/5 from 283 App Store ratings · 161 written reviews indexed
- Age rating: 4+
- Requires: iOS 12.0 · 9 MB
- Languages: American English
- Released: 2009-11-05
- Data updated: 2026-08-16
- Monetization: free
- User reviews in markdown: https://appshunter.io/ios/app/free42/id337692629/reviews.md

## What is Free42?

Free42 is a re-implementation of the HP-42S calculator and the HP-82240 printer.
It is a complete rewrite, not using any HP code, and it does not require an HP-42S ROM image.
Free42 is an Open Source project. The executables and source code are released under the terms of the GNU General Public License, version 2.
All third-party code used in Free42 is either in the public domain, or licensed under terms compatible with GPLv2, or used with the authors' permission.

## Key features

- HP-42S calculator simulation
- HP-82240 printer simulation
- Open source project
- No HP ROM required
- Complete rewrite

## What do users think of Free42?

Overall sentiment: positive

**Pros**

- 🚀 Faithful reproduction of HP42S
- 👍 Identical to physical calculator
- 👍 Runs all original programs
- 👍 Convenient to have on phone
- 👍 Haptic feedback on button presses
- 👍 Customizable skins
- 👍 Actively maintained and updated

**Cons**

- 🐛 Screen not filling entire display on newer devices
- 🔇 Configurable key click sound missing
- 🔇 Lack of loud click sound feedback

**Commonly reported bugs**

- Occasional issues with Solver function
- Store and Recall functions not working properly

**Most requested features**

- Display all registers (X, Y, Z, T, Last X) simultaneously
- Ability to share/transfer programs between devices
- Improved use of screen real estate on larger displays

## Recent user reviews (10 of 161)

All indexed reviews: https://appshunter.io/ios/app/free42/id337692629/reviews.md

### 5/5 — THE best calculator app

*2026-01-16*

The HP42s is one of the best calculators ever made.  I love Free42.  Plus42 is even better, which I was happy to buy to support the development of both apps.

### 5/5 — One request

*2025-10-27, version 3.3.9*

Big fan from forever ago. Had free42 on all my PalmOS devices, Android, PC, and i0S since my IPhone 1. However, the current version on iOS has the oldest built-in skins instead of the newest ones. Please fix?

### 5/5 — Super

*2025-08-23*

Use a 42s on my desk since many years. Nice to have one with me all the time! Thank you very much!

### 5/5 — Works great

*2025-01-30*

Wish there was a 41 CV version to replace my real one. But this is a good replacement.

**Developer response:** I'm glad you like Free42, but if you're specifically looking for an HP-41CV or CX emulator, i41CX is a good option.

### 5/5 — Would recommend

*2024-12-19*

This is an awesome RPN calculator, and does all the things you need and more.

### 5/5 — Best free app for thinking people

*2024-11-20*

This app is a service to mankind. Especially if you only speak RPN.

### 5/5 — Fantastic!

*2024-08-29, version 3.1.8a*

So nice to have this available.  I have always been a diehard HP RPN calculator fan.  This app is a faithful and convenient reproduction.

### 3/5 — Square root function not working

*2024-06-26*

Not sure why, but the square root function doesn’t seem to be working properly now.  Was working okay before. Not sure if other functions are also impacted.  Used to love this up until this happened

**Developer response:** It sounds like you're in BASE mode. Press EXIT repeatedly until there is no menu in the display, that should get you back to normal.
If that's not it, please contact me via email. It is a bit difficult to do tech support in review replies.

### 5/5 — RPN Rules

*2024-03-30*

My physical HP calculator died after 36 years and like many old engineers (I suspect), I wouldn’t use anything else. I tutor high school kids, with their TI 83’s and 84’s. Even though they can text much faster than me, an RPN calculator runs circles around them. 

This app is a perfect replica and I urge anyone who is allowed to use an iPhone to try it. It takes about 20 minutes to get used to a completely different way of operating, but you won’t ever go back to algebraic entry.

### 5/5 — Fantastic App!

*2024-02-09*

I have always used HP RPN calculators spanning a period of over fifty years and this App is a faultless rendition of the original calculator.

One really niggling problem is that the screen has rotated 90 degrees to landscape. Trying to get it back to portrate does not work. Any ideas? Any fix coming?

Ray Shead

**Developer response:** Please contact me via email.

## Frequently asked questions about Free42

### What does Free42 do?

Free42 is a re-implementation of the HP-42S scientific calculator and the HP-82240 printer. It provides the full functionality of these classic devices in a software application.

### Do I need an HP ROM image to use Free42?

No, Free42 is a complete rewrite and does not require any HP-42S ROM images to function. You can use it immediately after installation.

### Is Free42 free to use?

Yes, Free42 is an open-source project released under the GNU General Public License, version 2. It is completely free to download and use.

### What platforms is Free42 available on?

The provided data does not specify the exact platforms Free42 is available on, but as a simulator, it is likely designed for desktop operating systems or mobile devices.

### What are the main features of Free42?

The primary features include a faithful simulation of the HP-42S scientific calculator and the HP-82240 printer. It is also an open-source project, meaning its source code is publicly available and can be modified.

## Version history (last 5 releases)

### 3.3.12 — 2026-05-05

Fixed RLN and RRN for negative numbers in BSIGNED mode.

More accurate GAMMA for integer arguments.

### 3.3.11 — 2026-01-15

Added statistics sums to STAT->Σ and CATALOG->STAT menus.

### 3.3.10 — 2025-10-29

Fixed crash in menu logic.

### 3.3.9 — 2025-10-16

When a new program was created by inserting END, the new program could end up being locked initially. Fixed.

### 3.3.8 — 2025-07-03

Fixed a couple of rare crashes.

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## More apps by Thomas Okken

- [Plus42](https://appshunter.io/ios/app/plus42/id1597963622)
- [Life II](https://appshunter.io/ios/app/life-ii/id1621692220)

All apps by Thomas Okken: https://appshunter.io/developer/337692632

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-16.*